Advances in DNA testing are identifying the genes behind some common conditions. This introduces the possibility of screening for
these conditions and making appropriate decisions based on the screening results. It is important to understand what the results
mean and what is an appropriate response.

These conditions are
recessive,
which allows the incidence of the condition in offspring to be predicted. Parents are categorised as affected when they have the condition,
carrier when they are not affected but can pass on the condition, and clear when they are neither affected or a carrier.
The incidence of the condition in offspring will, statistically, be as follows...

Parents

Offspring

Parent 1

Parent 2

Clear

Carrier

Affected

Clear

Clear

100%

0%

0%

Clear

Carrier

~50%

~50%

0%

Clear

Affected

0%

100%

0%

Carrier

Carrier

~25%

~50%

~25%

Carrier

Affected

0%

~50%

~50%

Affected

Affected

0%

0%

100%

What you should ask your breeder

It is important to recognise that being clear or a carrier are both clinically normal conditions. If you want a puppy and have no intention
of breeding then a puppy that is either clear or a carrier will be equally acceptable. If you do intend to breed then you should still consider a puppy that
is a carrier, but you will need to ensure that it's mating partner is clear.

Breeding to eliminate all affected and carrier dogs might at first seem attractive, but this might lead to dogs with otherwise excellent characteristics being ruled out
unnecessarily. In addition, the narrowing of the gene pool that would result might throw up other conditions that are worse than those that are being targeted. With a growing
number of DNA tests becoming available it may become difficult to find two parents that are clear of all the conditions for which a test exists, which further underlines
the need to keep breeding from dogs that carry these conditions, provided that at least one parent is clear of each condition.

As long as your prospective puppy is clear or a carrier then other characteristics such as temprament and build should take precedence. Obviously, an affected puppy
should be avoided.

Testing for these conditions is not yet universal, and you may encounter breeders who do not test. Whilst their puppies may not be affected you cannot be
sure unless you know the status of the parents or the puppies. If a breeder is unaware of the tests that are available, or tries to convince you that testing is not
necessary, then you should carefully consider if they are the breeder for you. Any breeder asserting the testing status of parents or puppies should be able to
back this up with certificates to prove the status. Copies of these should be provided with your puppy, along with its pedigree. The results of dogs tested for PRA
can be found on the Kennel Club web site. Look for
Health Test Result Finder.
This paper by Cathryn Mellersh of the
Animal Health Trust explains why breeding from carriers is a sensible approach when done with knowledge and understanding.

Because CNM, EIC & PRA are recessive the status of an untested dog can be inferred from the status of tested dogs under some circumstances. In this table Clear, Carrier and Affected indicate actual test results. Clear by parents means that both parents are tested clear, Clear by g-parents means that both parents are themselves clear or clear by parents, and so on. Not clear by parents means that one or both parents is affected. Not clear by progeny & partner means that one or more progeny of the untested dog are not clear where the mating partner is clear.

There are several cases where both parents are not clear and so an untested dog has a 75% chance of not being clear, but these are not currently shown. Accuracy is subject to the integrity of the test results, the integrity of the breeders submitting them, the fidelity of Kennel Club data, and the robustness of the logic and programming used to make inferences. If you disagree with any inference please
let us know
and we will investigate and report back to you.

Our thanks to Gary Johnson of The Kennel Club for providing the source data.